I'm moving from LA to FL...we're driving straight thru. My mouse will be in a little carrier...?

You can use foods with a high water content like grapes, apples, melon, etc. Just make sure it really is 12 hours. I did this once when my water bottle broke at 11pm and I couldn't get another one until after work the next day. My rats were probably a bit thirsty but the fruit gave them enough hydration to stay healthy.

she probably would be ok for 12 hours but personally i wouldnt risk it. couldnt you get like a little cage? when i transport my rats i put them in a little hamster cage (one of the little ones that personally i think is too small for anything to actually live in) so then i can attach a water bottle to the side and a little house in the cage but because its a small cage its not like if the car crashes the rats guna be flying around some massive cage getting hurt.

Put in apple slices, carrots or any other fruit or vegetable that she likes. They have water in them and, in addition, will be a nice little treat. Have a fun trip. Make sure she won't be cold, an old, thick sock with the toe cut off will work.

Make sure that you stop several times along the way (whether to get gas/eat/sleep, etc.) and provide her water in a water bottle the entire time while you are stopped.

Wow every doesn't win in that situation. Keep the mouse in their they will be fine but when you stop or if you can trust her to not come flying out stick her water bottles tube at her, she will suck on it if she needs some.

Problem solved.

Drill a hole in the carrier so you can attach a water bottle.

Just pour some water in the tank. She'll get a nice workout by swimming, AND she'll have water :) Everyone wins!